264 Journal of Comparative. Neurology. 



on the other, it seems best for the present to retain the entire 

 system of terminology which is more typically urodelian. 



Druner, in his late work on Urodela, considers that the 

 lateralis component of this trunk is divided from the ganglion 

 into two distinct nerves which he calls " R. cutaneus mandibu. 

 laris lateralis" and " R. cutaneus mandibularis medialis." 

 These rami, which he describes in Salamandra, Triton, Meno 

 branchus and Proteus, are equivalent respectively to my r. 

 mentalis externus and r. mentalis internus. However, because 

 of the confusion of the terms "cutaneus" and "lateralis," 

 Druner's terminology cannot be conveniently used in treating 

 of the components of the nerves. 



The distribution of the r. mentalis seems to be very con- 

 stant in those Urodela which have been studied. The topo- 

 graphy of the head of Anura, however, is so modified- and 

 different from that of Urodela that it becomes very difficult to 

 make any useful comparisons of the nerve in the two types 

 from a study of advanced larvae alone. Owing to the great 

 number of lateral line sense organs, to their variableness and to 

 their transitory character in the larval stages, the first embry- 

 onic appearance of individual organs and their process of group- 

 ing must be studied exhaustively in a number of types before 

 valuable contributions can be made to the morphology of these 

 lateral line nerves of Amphibia. 



. 5. — The BrancJiial Ravii of the T. Hyoviandilnilaiis. 



The other two components of this trunk, the motor and 

 communis neurones, forn] the rr. jugularis and alveolaris in 

 Urodela, the rr. hyoideus and mandibularis internus of Anura. 

 These nerves are all interpreted by most authors as branchial 

 nerves. The exact relation which they severally hold to the 

 branchial clefts is of special interest. 



With regard to the branchial value of these rami in Nec- 

 turus, Platt ('96, p. 534) says: "The true post-trematic nerve 

 of the hyoid arch is the hyomandibularis and its ventral con- 

 tinuation, the 'internal mandibular.' Nor do I regard the 

 external mandibular nerve as the pre-trematic nerve of the 



